1. Field of the Invention
The invention is directed to the field of subsurface soil boring and more particularly to the field of generally horizontal boring of bores for the installation of utility items such as electrical cables and conduit, gas, water and other fluid-carrying ducts and pipes and similar items without disturbing the surface above such bores.
2. Description of the Prior Art
Other known steerable heads are formed of a single unit with a nose portion that is asymmetrical having jet nozzles and at least one surface of such nose portion set at an acute angle to the longitudinal axis of the head. The inclined surface of the nose portion is able to follow the contour of the cavity in which the head is placed when the head is advanced without rotation by its attached pipe string. Once the head is properly positioned in its new direction of travel, it is rotated and advanced again.
The asymmetrical nature of the head makes it rotate unevenly requiring additional advancing force and the presence of the inclined surface makes it wander and is subject to unwanted deflection and thus resultant changes of direction when an object or hard or compacted soil is encountered requiring numerous retractions and course corrections. One such head is shown in U.S. Pat. No. 4,674,579 issued Jun. 23, 1987, entitled Method and Apparatus for Installment of Underground Utilities by Edward Galler et al.